1. Field of the Invention
The present invention relates generally to evaluation boards and cable assembly evaluation methods, and more particularly to an evaluation board for evaluating an equalizer circuit to be mounted in a cable assembly and a cable assembly evaluation method using an evaluation board.
2. Description of the Related Art
In a cable assembly provided with a connector for high-speed transmission, the transmission characteristics of the cable assembly change depending on the length of a cable and the diameter of a signal line passing through the cable. In general, an equalizer circuit is mounted in the cable assembly in order to obtain good transmission characteristics.
Conventionally, in order to evaluate an equalizer circuit to be mounted in the cable assembly, multiple cable assemblies having respective equalizer circuits different in element constants from one another are prepared, and their transmission characteristics are measured. In order to facilitate the connection between a measurement device and the cable assemblies, the measurement device and the cable assemblies are connected through an evaluation board provided with a socket connector corresponding to the plug connectors of the cable assemblies and with SMA socket connectors for connection to the SMA plug connectors of measurement cables extending from the measurement device.
Conventionally, a test circuit switching method using a circuit that connects an internal circuit to and disconnects it from test terminals, the circuit being provided near an interface circuit with transmission channels, is proposed (Japanese Laid-Open Patent Application No. 2-284075).
However, in the case of evaluating equalizer circuits using the conventional evaluation board, it is necessary to prepare multiple cable assemblies having respective equalizer circuits different in element constants from one another, thus resulting in poor efficiency. Further, in the case of changing the constants, it is necessary to disassemble the plug connectors and change elements, which is not easily performable.
For the above-described reasons, equalizer circuits are not evaluated with efficiency.
Further, it is impossible to evaluate equalizer circuits with accuracy only with simulations because errors occur at the time of actual mounting.